Furnace-lining material and process for preparing same.



0. J. BARR.

FURNACE L|N ING MATERIAL AND PROCESS FOR PREPARING SAME- APPLICATIONFILED DEC. 25; I914.

Patented NOV. 28, 1916.

COHESIVE ENVELOPE DDLOMITE Emma/two C. J. BARR CHARLES J'. BARR, OFBIRMINGHAM, ALABAMA, ASSIGNOR TO ALLEN S. DAVISON COMPANY, OFPITTSBURGH, PENNSYLVANIA,.A CORPORATION OF PENNSYLVANIA.

PURN AGE-LINING MATERIAL AND PROCESS FOR PREPARING SAME.

Application filed December 26, 1914. Serial No. 879,146.

To all whom it may concern Be it known that I, CHARLES J. BARR, acitizen of the United States, residing at Birmingham, in the county ofJefferson and State of Alabama, have invented certain new and usefulImprovements in Furnace- Lining Material and Process for Preparing Same,of which the following is a specification.

My invention relates to the production of a refractory material forforming and repairing the bottoms or linings of furnaces, and my objectis to produce an artificially prepared substitute for magnesite which islargely used in making furnace bottoms.

In the operation of basic open hearth furnaces, burned magnesite fromAustria-Hungaryhas been found to be the only material which issatisfactory for making refractory furnace linings which will bondtogether in a way and to resist the washing action of the bath. Thiscalcined Austrian magnesite is not a pure magnesium oxid, but containssufficient fluXing material in a form of contained impurities, such assilica and iron oXid, to give it this essential cohesive property. Puremagnesia does not bond. I roughly estimate that one hundred thousandtons of this imported magnesite are now used by the steel makers of theUnited States at an average delivered cost of twenty dollars per ton.

It is an object of the present invention to produce a granularrefractory material suitable for lining and repairing basic open hearthfurnaces capable of replacing Austrian magnesite for this purpose, usingnative materials.

We have a large native supply of dolomite which is cheap, and thisdolomitic hme has been used to a considerable extent with magnesite toreduce the quantity of the latter in the bottom material and lining,particularly of open hearth or basic steel furnaces. Dolomite, which isa double carbonate of lime and magnesia furnishes a calcined productcontaining both lime and magnesia which is as highlyrefractory ascalcined magnesite, but it dices. not contain suflicient fiuxingmaterial in the shape of silica or iron oXid to sinter and bond, or tobecome sufiiciently plastic in the furnace heat to form a co-' hesivelining or bottom that will not wash and disintegrate, The calcineddolomite Specification of Letters Patent.

Patented Nov. 28, lore.

alone does not bond in the furnace; and it is not as weather proof ascalcined magnesite, taking up water and CO on standing for any length oftime after burning.

The object of my invention ,is to so treat the dolomite lime, or otherlike refractory material in which the requisite fiuXing material is notpresent, as to give it the cohesive or bonding property necessary tomake a firm bottom; and to produce the treated dolomite at a small costso that the product may wholly replace the imported Austrian magnesite.

According to my invention I coat granules or grains of calcined dolomitewith an envelop or glazing of a somewhat'less refractory material havingthe quality of fusion or .cohesion under furnace heat, so

that in use the coated grains of dolomitic I high to thoroughly shrinkthe material."

The quantity of coating material used with the dolomite material varieswith the character of each material and of the operating conditions ofthe furnace in which the pre pared bottom or lining material is to beused. It may be stated, however, that the object of my invention isattained where the coating is sufficient in quantity and of a quality toform an effective bond for the incased grains of dolomitic lime.

In the accompanying drawings: Figure 1 illustrates an apparatus which Ihave used successfully for carrying my process into effect; and Fig. 2is an enlarged detail sectional view through a portion of a furnacebottom lined with my prepared material.

The crushed or granular dolomite is fed into the upper end (not shown)of a rotary kiln 1 of the ordinary type and passes downward therethroughas a traveling stream again t flame gases a d flame pa s ing in theopposite direction. In their passage the granules are highly heated anddeprived of their CO and converted into dolomitic lime and thoroughlyshrunk. The coating material occurs in the zone of highest heat and asthe grains or granules pass through this zone they pick up such coatingmaterial as they roll and each granule is substantially coated when itfalls from the kiln. The coating material is fed from hopper 2 by anysuitable feed mechanism into pipe 4 through which it is carried into thehot zone at the mouth of the kiln. This pipe may be, as shown, connectedto pipe 5 which carries the fuel blast into the kiln. Under the kilnheat, the coating material fuses or softens and adheres to and coats thesurface of the very hot granules of calcines. The coating process shouldbe so conditioned as not to cause the coated grains to cohere in A thekiln, but to deliver them as separate coated particles which are readyto be applied,in the same manner as calcined magnesite. to form thefurnace bottom.

In Fig. 2 I show, enlarged, a section of furnace bottom lined with thepresent material in which the grains 6 are shown each coated with anenvelop 7 of slag, flue dust, ground iron ore, or a like material, whichenvelops have fused under the furnace heat and bonded the grains 6firmly in place in the furnace bottom. 5

A great advantage of my invention is that the coated grains of magnesiumcalcium oxids will absorb moisture much less rapidly than theunprotected dolomitic lime and hence my material can be stored andshipped. Granular calcined dolomitic lime made in accordance with theusual practice,

that is, without the use of the present invention, ordinarily must beproduced at the point of use since unprotected dolomitic lime reabsorbsmoisture and carbon dioxid' on shipment or storage.

'My process may be extended to the treatment of other highly refractorybodies than dolomite, such as Californian or Grecian magnesite whichyield pure magnesia on calclning'and do not contain sufiicie'nt fluxingmaterial, such as silica or iron oxid, to

set or bond in the furnace bottom and produce a permanent lining.

When I refer to dolomite herein I mean to,

include such other bodies.

What I claim as new and desire to secure by Letters Patent, is

1. An artificially prepared granular furnace bottom material consistingof grains of non fluxing refractory material separately coated with aless refractory normally noncohesiveenvelop whichis sufliciently fusible1n furnace heat to set and permanently bond the said grains ofrefractory material.

2 An artificially prepared granular furnace bottom material consistitngof roasting grains of dolomite and coating the roasted grains with anenvelop of slag, to set and bond the dolomite.

8. The hereindescribed process for manufacturing a furnace bottommaterial which consists in roasting dolomite grains and coating the hotgrains with a less refractory envelop which will fuse and set in thefur- I dolomite.

5. As a new material, a body of granules of basic hard burnt material,such granules being coated and sealed with a layer of less refractorymaterial adapted to serve as a bonding agenton exposure to hightemperatures.

6. As a new material, a body of granules of hard burnt magnesian lime,such granules being coated and sealed with a layer of less refractorymaterial adapted to serve as a bonding agent on exposure to highertemperatures.

7. .As a new material, a body of granules of basic hard burnt material,such granules being coated and seated with a layer of less refractorysilicious material.

8. As a new material, a body of granules of hard burnt'magnesia'n lime,such granules being coated andsealed with a layer of refractorysilicious material.

9. As a new material, a body of granules of basic hard burnt material,such granules being coated and sealed with a layer of basic open hearthslag.

, 10. The process of producing materials .for furnace linings whichcomprises agitat- 'ing granules of basic refractory material at a hightemperature in the presence of v fine and less refractory material untilsuch refractory material film coats the surface of such granules. I p

11. The process of producing materials for furnace linings whichcomprises agitating granules of basic refractory material with powderedbasic open hearth slag at a high temperature until such open hearth slagfilm coats the surface of such granules.

12. The process of producing materials for furnace linings whichcomprises agitating granules of dolomitic lime with less refractorymaterial at a high temperature until such refractory'material film coatsthe surface of such granules.

13. The process of producing materials for furnace linings whichcomprises agitating granules of dolomitic lime with powdered basic openhearth slag at a high temnacemi perature until such open hearthslag-film coats the surface of such granules.

14. A furnace lining material, comprising a substance containingmagnesium oxid, the particles of the said substance being coated with amaterial which protectsthe particles against atmospheric conditions.

15., A furnace repair material, comprising a substance in the form ofgranules which contain magnesium oxid, said granules being coated With amaterial Which protects the granules against atmosphericaction.

16. A material for the repairing of furnace linings, comprisingparticles of calcined dolomite, the particles of the latter being coatedwith an adhering layer of material which protects them from moisture;

In testimony whereof I aflix my signature in presence of two Witnesses.

CHARLES J. BARR.

Witnesses: R. D. JOHNSTON, Jr., NoMIE WELSH.

